It is well known to store energy in an energy output system wherein that energy is recovered and made useful in some form. Flywheels and batteries have been used in various combinations with primary energy output systems to accomplish this result. It is also known to use compression cylinders for the purpose of storing energy for driving a system during high-low conditions. Examples of such systems are shown in U.S. Pat. Nos. 3,693,351, 3,910,043 and 4,037,409.
U.S. Pat. No. 3,693,351 discloses an anti-pollution regenerative compressed air system. Here, the primary driving source is compressed air. A secondary energy source is established by compressing air during periods while the automobile is not drawing full power through the use of a combination of a pressure booster tank and high pressure accumulator tank. There is no provision in this prior art system, however, for storing power that is not otherwise used to drive the mechanical output in the primary piston assembly.
U.S. Pat. No. 3,910,043 discloses an energy accumulating system having a combination of a flywheel and hydraulic primary pump/motor. This hydraulic transmission assembly has a control system including pedals and/or levers which control the flywheel/pump complex in a manner to determine the pressure useful in the hydraulic primary power circuit.
U.S. Pat. No. 4,037,409 shows a gas turbine engine used in combination with a flywheel and hydraulic transmission assembly. The flywheel and the hydraulic transmission are driven by the same input shaft leading from a gas turbine engine. Thus, all of the energy generated in the motor unit of this system is used to rotate the drive shaft. At the same time, the energy required to turn the wheels of the vehicle will not always require all of the energy of the hydraulic motor.
Other well known compressed air engines have various types of auxiliary air compressors and secondary power supplies including batteries connected thereto. See particularly U.S. Pat. Nos. 3,765,180, 3,847,058 and 3,925,984.
U.S. Pat. No. 3,793,835 shows a variable rate hydraulic transmission system wherein the pressure on the hydraulic fluid is maintained generally constant by a gaseous medium. However, this system is static and the compressed gaseous medium supply acts as a shock absorber providing an equilibrium balance to the hydraulic fluid system. The compressed gaseous medium operates in conjunction with the well known hydraulic fluid accumulators designed for this purpose.
Most recent efforts to provide a system for storing kinetic energy in a vehicle is disclosed in U.S. Pat. No. 3,903,696. Here, a hydraulic system is used to collect and store energy upon the braking of the vehicle. The hydraulic accumulator is connected in a particular way to the hydraulic fluid reservoir with a capacity for the operator to selectively permit fluid flow in the system to store energy on braking of the vehicle and release the stored energy to accelerate the vehicle. However, there is no provision for recovering any of the hydraulic fluid energy not required during the operation of the mechanical output; namely, the vehicle wheels during operation of the system.
Energy transfer systems are used for the purpose of changing the form of any material such as grinding grain, cutting wood chips, baling cotton or compressing old automobiles. A known system comprises a full tree, wood chipping machine having an engine operating at varying energy levels depending upon the size of the trees being chipped. An additional engine of equal size was installed when it was discovered that the initial single engine system was using too much fuel. In this instance, both engines are operated at optimum efficiency modes at all times with the combined engines using one-third as much fuel as the original one engine used alone.
Conventional drive energy transfer systems in vehicles and other machinery, couple the power source directly to the driven implement using gears, shafts, chains or belts. Thus, a fixed relationship is established between the power transferred to the implement and the speed of the power source. This relationship is a function of the gear ratios and the like selected for the transmission assembly. The power source must be large enough to provide the amount of power that is required during the peak demand periods in such a system. Typically, peak demand periods constitute a very small portion of the total operation time. In other words, the systems are generally overdesigned with respect to the average operating capacities. Clearly, severe efficiency penalties result with the power source operating in an inefficient load range most of the time. With the overdesigned power source, there is an excessive weight demanding further wasteful power consumption.
As a vehicle, or other implement, is accelerated to its working speed, much of the energy from the power source is converted to kinetic energy. The kinetic energy can be mathematically related to the mass of each moving part and the square of its velocity. Such kinetic energy is appreciable in the operation of vehicles and heavy machinery. Such energy is wasted through the use of braking systems and other frictional forces. Even vehicles that motor their engines for braking, transfer the kinetic energy of motion into wasted energy at the expense of additional fuel use. None of the kinetic energy is captured. Consequently, the power source must supply the entire amount of energy required for each acceleration and load cycle.
As noted above, prior art attempts have used a simple hydraulic drive system with a hydraulic accumulator to store excess power from an internal combustion engine. This is an attempt to use or store the extra power that could be provided by the power source when workloads are low and during periods of deceleration. The accumulator in such a prior art system has only a finite capacity for energy storage. Thus, there is an intermittent cycling of the engine to charge the accumulator. Once maximum hydraulic working pressure is reached in the accumulator, the capability of storing any further energy disappears and the charging engine must be stopped. When the accumulator pressure drops below the minimum, the charging engine is restarted. With this fluctuation in hydraulic pressure, axial torque and speed cannot be smoothly controlled. Consequently, the repeated on and off cycling causes extreme wear and inefficient operation of the engine.
Kinetic energy cannot be effectively recaptured and stored in the accumulator type system if the engine is running. That is, the engine would be driven in a motoring mode which absorbs energy. Furthermore, the accumultor is unable to accept additional power input when it is near its maximum pressure. When the engine is not running, it cannot add power to the power delivered by the accumulator for maximum loads. The vehicle with the accumulator type system must carry the weight of the engine even when it is not contributing power to the system. An electronic processor becomes necessary to effect the complex control for the system. Failure of such a processor renders a vehicle inoperable and irreparable by the average driver or mechanic.